Wireless Home Networking - Index of

Chapter 2: From a to n and b-yond
output of less than 30 dBm (one watt). Government agencies around the
world regulate the maximum power output allowed. APs for home use
generally have power outputs in the range of 13 dBm (20 mW) to 15 dBm
(31.6 mW). The higher the power rating, the stronger the signal and the
better range your wireless network will have. Some wireless networking
equipment manufacturers offer add-on amplifiers that boost the standard
signal of the AP to achieve a longer range. We talk about boosters
in Chapter 18.
� Antenna gain: The AP’s antenna and the antennas on the other devices
on the network improve the capability of the devices to send and receive
radio signals. This type of signal improvement is gain. Antenna specifications
vary depending on vendor, type, and materials. Adding a highergain
antenna at either end of the connection can increase the effective
range.
� Antenna type: Radio antennas both send and receive signals. Different
types of antennas transmit signals in different patterns or shapes. The
most common type of antenna used in wireless home networks, the
dipole antenna, is described as omnidirectional because it transmits its
signal in all directions equally. In fact, the signal from a dipole antenna
radiates 360° in the horizontal plane and 75° in the vertical plane, to
create a doughnut-shaped pattern. Consequently, the area directly above
or below the antenna gets a very weak signal.
Some types of antenna focus the signal in a particular direction and are
referred to as directional antennas. In special applications where you
want an AP to send its signal only in a specific direction, you could
replace the omnidirectional antenna with a directional antenna. In a
home, omnidirectional is usually the best choice, but that also depends
on the shape of the home; some antennas are better for brownstones
and multifloor buildings because they have a more spherical signal footprint
rather than the standard flatish one.
� Receive sensitivity: The receive sensitivity of an AP or other wireless networking
device is a measurement of how strong a signal is required from
another radio before the device can make a reliable connection and
receive data.
� Signal attenuation: A radio signal can get weaker as a result of interference
caused by other radio signals because of objects that lie in the
radio wave path between radios and because of the distance between
the radios. The reduction in signal is attenuation. Read through Chapter 4
for a discussion of how to plan the installation of your wireless network
to deal with signal attenuation.
To replace or add an antenna to an AP or other wireless device, you need to
have a place to plug it in — as obvious a statement as that is, many antennas
aren’t detachable, and you can’t add another antenna. Some access points
use reverse TNC connectors that let optional antennas be used in 802.11b/g
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